The seed of
this book was actually a mere private survey of current
angiosperm phylogeny and taxonomy containing lists of the
features characterizing the different clades. At first, that seed
was not intended to grow into a publication, neither at the
world-wide web nor as a printed book. Nevertheless, it constantly
expanded and, after having been offered a potential website by
Professor Birgitta Bremer at the Hortus Bergianus (the Bergian
Botanical Garden) in Stockholm, I decided to further extend the
text and make it readable for other people than myself.
Hopefully, the book may be used by any educated person interested
in advanced angiosperm systematics. However, it is not designated
for beginners. Nevertheless, the book is provided with glossaries
and these should facilitate even for non-specialists the
understanding of the text.

The book
may also be looked upon as a part of the digital Tree of Life (in
Swedish ‘Livets Träd’), which was put together by me and Ronny
Larsson, professor of systematic zoology at the University of
Lund, and made available to the public in 2006. The Tree of Life
covers all known major lineages of organisms, although the
chapter dealing with flowering plants was abbreviated at that
time.

The present book, The Phylogeny of Angiosperms,
represents a first preliminary version, certainly suffering from
an enormous amount of errors and other deficiencies. Hence, I
would be grateful to the readers for all comments and suggestions
of improvements. Any opinions about the contents can be forwarded
directly to the author’s e-mail address:
.
The presentations of the taxa are especially in need
of additions and corrections. One of the most important aims of
this book is to provoke scientists to intensify the research on
the numerous poorly known clades. For this purpose, I have
attached a list of missing characters for the taxonomic groups
treated in this book.

Angiosperm
systematics has undergone an entire revolution during the last
twenty years. This enormous progress is mainly due to the
advancement of molecular approaches, computer technology and
cladistics theory. The recent renaissance of plant morphology has
also provided an increasing amount of new data. Phylogenetic
analyses of nearly all main lineages of flowering plants have
been carried out at an accelerating speed. If this effort
continues, utilizing ever more nuclear genes in particular, the
Angiosperm Tree of Life will hopefully be almost completely
covered within the next few decades, at least when speaking of
the chief lineages of extant flowering plants. The main branches
of this phylogeny now seem to be clarified, new analyses more or
less confirming and solidifying most of the cladistic hypotheses
suggested during the last fifteen years. Yet an enormous amount
of genera are not or only poorly investigated.

During my career as a biological systematist the views on
flowering plant systematics and evolution have fundamentally
changed more than ever before. Hence, it has been and still is an
extremely fascinating period for an evolutionary biologist. At
the same time, we become more and more aware of the fast growing
threats against Earth’s biodiversity and that future generations
will probably not be able to enjoy the incredible multiplicity of
species that surround us today. Often, the threat is most severe
against such taxa which are critical for our understanding of the
phylogenetic patterns and, consequently, for the evolutionary
processes. Species-poor lineages with very limited distributions
are often sister-groups to species-rich clades with considerable
genetic diversity. Such old yet tiny lineages are crucial for
character polarization and our understanding of the evolutionary
processes of their large sister-clades. Examples areAmborella
trichopoda (sister to all
other angiosperms),Petrosaviaceae (sister to the chief clade of monocotyledons),Gunneraceae (sister toPentapetalae),Pennantia (sister to
all otherAraliales),Tepuianthus (sister to the remainingThymelaeaceae),
and the tiny lineages withinStaphyleales (a basal
clade amongMalvanae).

We have
come to a point where comprehensive and even detailed surveys of
the current state of knowledge may be produced. This book is such
a synthesis of current information, both retrospective and
forward-looking.

Results
from systematic-phylogenetic research are overflowing at an
increasing rate. This means that a traditional paper-book that
tries to be highly updated will become hopelessly outdated
already at the moment of printing. Digital publication is a
simple solution of such a problem. Any change in the text may be
made quickly, as soon as new information is available. The book
is as easily accessible as any web-carried data. Moreover, it is
a low-cost alternative – free to use.

Among all those sources that I have utilized for
compiling the information in this book, I will here mention only
a few of the many outstanding references: Kubitzki & al.
(1993 onwards)The Families
and Genera of Vascular Plants; Nickrent (1998 onwards)The Parasitic Plants Website; Stevens & al. (2001 onwards)The Angiosperm Phylogeny
Website; and – for the
nomenclature of suprageneric names – the websites and articles by
Dr James Reveal (the University of Maryland).

Many clades are very difficult to define using
morphological features. This is due to the extensive degree of
homoplasy found among angiosperms. These clades are nevertheless
recognized as monophyletic in most cladistic analyses and thus
have to be accepted, even if they cannot be identified in the
field using traditional approaches. Some well-known examples
areCelastraceae,Lamiaceae,Plantaginaceae,Ranunculaceae,Ruscaceae,Salicaceae, andScrophulariaceae.
Homoplasies are rules rather than exceptions among angiosperms.
All types of characters – even molecular characters – are subject
to parallelisms and reversals. Some genes coding for anatomical,
phytochemical or other features may be switched off rather than
simply lost, which means that they may be easily reacquired over
and over again.

Information
on species number of the groups is often very approximate and
uncertain, and, of course, depends on the divergent views on
species definitions and generic delimitations among different
taxonomists. As an example, some authors may have a very wide
species concept, whereas others may prefer a restricted concept.
As a result, the number of species within the genus in question
may vary between ten and more than fifty. However, such
differences of opinions will certainly always exist.

The present
book is subdivided into:

• An introduction to the angiosperm phylogeny and taxonomy
used in this book. This chapter is named
Magnoliopsida.

• Chapters describing all major clades of
angiosperms.

• An alphabetical list of accepted generic names and their
synonyms.

• Two different glossaries: one general glossary explaining
morphological, cytological, anatomical, embryological and other
terms; and a second glossary dealing with phytochemical
terminology.

• Finally, I have also included lists of unknown character
states for the different clades in alphabetical order. According
to my opinion, this is not the least important part of the book.
A goal of utmost importance is to present what we donotknow. Some character complexes, such as embryology and
ultrastructural features, are particularly poorly studied for
numerous taxa. Many character states are unknown for critical
taxa such asAmborella. I have
already mentioned the importance of having sufficient knowledge
of the crucial sister-groups of larger lineages, since these are
critical for our understanding of phylogeny and character
polarization. In general, polarization is very difficult and
often impossible for angiosperms, since their relationship to
other seed plants remains obscur.

I have
deliberately left out some types of information:

• Information about the hypothetical ages of clades and
nodes are excluded, since these are still very unreliable and
depend on our knowledge of the phylogeny in question and the
different methods of age determination used. In too many cases
there may be substantially disparate estimates of the age of a
specific clade. The issue is also intensively debated. In
particular, the constrained (fossil-based) ages are usually much
younger than the relaxed ages. Moreover, the identification of
(often fragmentary) fossils is usually more or less
uncertain.

• Literature references will only exceptionally be found
within the text. Instead, a list of literature is given at the
end of each main section. It is my hope that the reader will find
the text somewhat easier to follow, instead of finding extensive
lists of references packed in the middle of the sentences.
General references, dealing with a larger part of the angiosperm
system, are found within the chapter Magnoliopsida.

• Information on branch support, sequenced genes and
cladistic algorithms are not presented in the phylogenetic trees
in this book. Such important data are given in the original
publications; references to these will be found in the literature
lists.

• Historical sections or comparisons with previous views
and ideas are not included here. Such information may be found in
almost all other textbooks of plant systematics and my opinion is
that providing such a chapter here would not add any new
knowledge beyond those already published and comparatively
accessible to the reader.

• Sections on methodology or cladistic theory are beyond
the scope of this book. Excellent descriptions of different
technical approaches and phylogenetic theories are provided in
numerous publications.

• Drawings (other than phylogenetic trees) are not included
in the first version of this book. Instead, a large and growing
number of colour photos are provided.

In this
preface I will also take the opportunity to explain some of those
principles that have been the guidelines in my present account of
the flowering plants.

The first
and foremost aim is to present a phylogenetic system covering all
main clades of flowering plants and only accepting monophyletic
groups.

Ranks in the traditional sense (i.a. family, suborder,
order, and subclass) are not used in this book. Instead, the
concept of “rank” is used only in reference to clades. In other
words, the subdivision of a group exclusively follows the
sequence of branches in a phylogenetic tree. According to
theArticle
3.1of the Phylocode, the
nomenclature is independent of categorical rank. A phylogenetic
rank is unimportant for the formal naming and should not
influence the spelling of the name of the group. Another
principle that I have tried to follow is the one stated in
theArticle
3.2, namely that synonymy,
homonymy and precedence are independent of categorical rank.
Finally, I have not followed the traditional nomenclatural system
of rank-dependent suffixes on the clade names, since this would
soon result in a hopelessly large amount of different suffixes.
In traditional systematics using traditional ranks, this would
mean that one has to change the suffix (often the name as well)
as soon as the clade becomes less alternatively more
inclusive.

The reader will soon discover that I have promoted a more
narrow “family” concept (I apologize for here using this
specified rank according to the custom of a more traditional
taxonomy) than, e.g., the now generally accepted system of APG
III (2009).Iridales (Asparagalesof APG),
for instance, are here divided into 28 subclades (“families”).
Instead, I have followed the principle of “too much is better
than too little” in presenting the information.

All clade
names should follow the principles of priority. This is actually
stated in article 16B.1 of the International Code of Botanical
Nomenclature: “In choosing among typified names for a taxon above
the rank of family, authors should generally follow the principle
of priority.” Unfortunately, this recommendation is usually not
followed for suprafamilial ranks in the traditional
taxonomy.

The
selection of cladograms and summary trees is, of course, very
subjective. Yet I have tried to choose the latest available
phylogenetic trees founded on as many taxa and characters
(usually only molecular data) as possible, and consisting of
reasonably supported clades. In many cases, I have simplified the
cladograms in order to make them handier for the reader, although
trying not to exclude more than a minimum amount of information.
If an original cladogram is too large for a single page, I have
partitioned it into two or more pages.

A
classification should follow the prevailing and generally
accepted phylogenies as closely as possible. Moreover, a
classification should be

• universally applicable

• hierarchical

• informative

• predictive

If
following the phylogenies as closely as possible, these rules
will be complied with.

Acknowledgements

I express my special
gratitude to the staff at the Hortus Bergianus (the Bergian
Botanical Garden) at the University of Stockholm for putting a
website at my disposal. A laborious task was – and still is –
spent by Dr Niklas Wikström (Hortus Bergianus, Stockholm) in
creating and administrating this site.

I am
particularly indebted to Dr Peter F. Stevens at the Missouri
Botanical Garden and the University of Missouri at St Louis,
whose tremendous and invaluable Angiosperm Phylogeny Website has
been one of the most important sources of information. This
formidable website will be repeatedly cited in the
text.

But first
and foremost I am grateful to all those indefatigable and often
self-sacrificing botanists, collectors and amateurs of all times
who have devoted their lives to the noble aims of gathering
plants and data. Thank you!